blessing



J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION FILED MAR Z, 1917.

Reissued Mar. 22, 1921. 15,068.

10 SHEET HQJ.

J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION FILED MAR 7, 1917- 15,068. 10 SHEETSSHEET Reissued Mar. 22,1921.

QPE NA A kmw AA h kw q 1 Q5 5 J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION FILED MAR. I. 1917.

Reissued Mar. 22, 1921. 15,068.

10 SHEETSSHEET 3- Q m M m ,R R Q g q E i WEEK);

- [nUEL-LZUI" 7 HZTQZIEQ J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION FILED IIIAII. 7, I917.

Reissued Mar. 22, 1921. 15 ,068.

10 SHEETS SHEET 4.

HZZurngy J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION HLED MAR. 7. 1917.

Reissued Mar. 22, 1921. A 15 ,068.

l0 SHEETSSHEET 5.

HZ Z51" n5 W J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATTON FILED MAH r, 1917.

Reissued M111. 22, 1921. A 15 ,068;

10 SHEETSSHEET 6- 1 g [L'LU z-LZUF @5 2 a: 53%

. J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION FILED MAR. 7, 19]?- 15,068. 10 SHEETS-SHEET I.

Reissued Mar. 22, 1921.

i am .l. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION FILED MAR. 7. 1917.

Reissued Mar. 22, 1921. 15 ,068.

10 SHEETSSHEE'I B.

J. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS. APPLICATION FILED MAR. 1, 1917.

Reissued Mai. 22, 1921. 15,068.

10 SHEETSSHEET 9.

r v 1171521201 42 @w .l. G. BLESSING.

AUTOMATIC TELEPHONE SWITCHING APPARATUS.

APPLICATION FILED MAR. 7. 1911.

Rejssued Mar. 22, 1921. A 15 ,068.

10 SHEETS-SHEET 10.

A [must-afar 2 l? UNITED STATES PATENT OFFICE.

JOHN G. BLESS IN G, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRICCOMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

Original No.-1,145,542, dated T 0 all whom it may concern:

Be it known that I JOHN G. BLEssING, a citizen of theUnited states ofAmerica, and resident of Chicago, Cook county, Illinois, have inventeda' certain new and useful I-mprovement in Automatic Telephone SwitchingApparatus, of which the following is a specification.

automatic switch is of the kind known as a selector. In other cases theline thus found will be a subscribers line, and in that event theswitch-will be. of the kind ordinarily known as a connector. Therotation of a selector is, of course, purely automatic so that an idletrunk line is automatically selected. The rotation of the connector is,however, directly under the control of the calling subscriber, or thecalling operator, if the system be semi-automatic.

Ordinarily, the callin'g.mechanism, by which automatic switches ,of thisor any other suitable character, are controlled, must be operatedsomewhat slowly, or at least not toofast, so that the transmission ofthe electrical impulses will properly control the switches. This, ofcourse, in some cases, means that the calling operation will tend todelay the work of the operator or other person making the call, or atleast absorb too much of the time and effort of such person, owing tothe more or less deliberate manner in which the manual manipulation ofthe calling mechanism must be performed, for the reasons stated. Take,-for example, the case of the system 1n which the automatic switches arecontrolled by the manual switchboard operator. In a system of this kind,and with the ordinary calling mechanism, the operator would be givingover a large amount of time and effort to the operation of the callingmechanism whereas, if the said mechanism could'be operated very quickly,the call could be made with Specification of Reissued Letters Patent.Rei d 31 1 July 6, 1915, Serial No. 586,530, filed October reissue filedMarch 7, 1917, Serial No. 153,216.

22, 1921. 11, 1910. Application for despatch, and the operator wouldthen be free to do something else. a

It has been recognized, therefore, that, for various reasons, a callingmechanism that could be operated manually as fast as the operator iscapable of working, and which would then more slowly transmit theelectrical impulses leaving the operator, or other person, free to bedoing something else, wh le the call is being transmitted, would hedesirable,and some effort, so I understand, has been made along thisline. So far, however, I do not understand that the results have beenentirely satisfactory.

Generally stated, therefore, the object of my invention is to provide animproved and h ghly efficient calling mechanism of the kind in which themanual operation thereof is performed swiftly and as fast as theoperator or other person is capable of workmg; and in which, while suchperson is then free to do something else, the electrical im- ,pulses aretransmitted more slowly and in to properly control the manner calculatedthe automatic switches.

The special object of my invention is to prov1de a calling mechanism ofthis general character in which a single set .of keys is sufiicient forcalling any number having a plural ty of digits-that is to say, havingprovisionwhereby any key may be pushed or actuated more than once duringthe set ting up "of the call, in all cases where two or more of thedigits of the called member are the same, thus rendering it unnecessaryto employ more than the single set of keys for controlling the, deviceby which the electrical impulses are "transmitted.

A further object is to provide an improved method of spacing apart thedifferent digits of any called number involv-- hind the operation of thekeys or push but-- spring, and whereby transmission ofthe impulses mayfollow at a variable distance betons by which the mechanism iscontrolled in accordance with the called number.

A further object is to provide improved means for varying the number ofimpulses necessary for each digit of the called nu1nber, involving acircular series of movable contacts, and means for skipping a number ofcontacts for each digit of the called number, and for actuating one ormore contacts between the groups of skipped contacts, to space thedigits apart, which skipping and actuating means are controlled by a setof keys or push buttons.

It is also an object to provide certain details and features ofimprovement and combinations tendmg to increase the general efficiencyand serviceability of a telephone exchange system of this particularcharacter.

To the foregoing, and other useful ends, my invention consists inmatters hereinafter set forth and claimed.

In the accompanying drawings Figures l, 2 and 3 taken together showacomplete circuit connection between a calling manual substation A and acalled automatic substation A in a system embodying the principles of myinvention. Fig. 1 shows the connection extended from the manualsubstation A through the operators cord C to a trunk line leading to anautomatic exchange. In Fig. 2 there is represented an automaticswitching apparatus consisting.

of a line or trunk switch D, master switch E and selector switches F andH. In Fig. 3 there is represented a connector switch -I, and a lineswitch I) which is individual to the line of substation A Fig. 4: is adiagrammatic representation-of a system embodying the principles of myinvention.

Fig. 5 is a plan view of my improved operators calling mechanism.

. Fig. 6 is a sectional view on the line 6-6 of Fig. 5, but showingnothing beyond the.

line 7--7.

Fig. 7 7-T of Fig. 5, but showing nothing beyond line 9-9.

Fig. 8 is a view of a section on line 8-8. but showing nothing beyondline 9--9.

Fig. 9 is a view of a section on line 9-9, but showing nothing beyondline 77.

Fig. 10 is a view of a longitudinal section on the line 10 -10 of Fig. 5

Figs. 11 to 18. inclusive, are detail views of'parts of the apparatus atdifferent stags of its operation.

Fig. 19 is a view representing the circuit connections of the callingdevice.

Fig. 20 is a diagram showing the principle of the mechanism insimplified form.

is a view of a section 011 the line I shall first describe 'theconstruction and method of operation ofthe operators calling devicewhich is illustrated in Figs. 5 to 19, inclusive. In these figures 2represents a suitable base near one end of which are mounted two uprightposts 3 and 4 (Fig. 6), near the top of which are secured two flat crosspieces 5 and 6. In these cross pieces there are mounted'ten push buttons7. Each of these push-buttons is normally held in its uppermost positionby a spring 8 The lower ends of the push buttons 7 are preferablyflattened and extend into openings in the cross piece 6, butdo notproject below the lowersurface thereof. To each of the push buttons 7there is secured alaterally projecting arm 9 whichnormally engages theso I under side of the plate 5 to limit the upward motion of the button.When any button is pressed, its arm 9 is adapted to register with adiagonal slot in a bar 10. The bar 10 is loosely'mounted at each end ina block 11, so that whenever any of the buttons 7 are pressed, the saidbar will be forced to slide toward the left; as shown by dotted lines inFig. 6.

Near the center of the base 2 there is mounted a drum consisting of acentral portion 12 (Fig. 10), two end plates 13 and 14 and an outercasing 15. The plates 13 and 14 are provided near their peripheries witha number of slots'in which are loosely supported the endsiof a number offiat pins 16. Inside the drum these pins are provided near each end witha shoulder 17 which limits their motion in either direction. In orderthat the pins 16 may not slidetoo easily, each pin is provided with aU-shaped spring 18, one end of which is secured in a slot in the centerpiece 12, while the other end bears against the side of the pin. The

'lateral pressure of this spring on the pin produces sufiicient frictionto prevent the said pin from being affected by jars or vibration.Extending through the center of this drum there is a hollow shaft 19, tothe ends of which are secured the arms 20 and 21. At its outer end thearm 20 is bent at right angles toward the plate 13 and is beveled, asshown in Figs. 11, 12 and 13, so that any projecting pins which itpasses in its revolutionwill be forced back, flush with the plate 13. vThe arm 20 also carries two contact springs 22-and 23, Fig. 9. The endof spring 23 is V-shaped, so that whenever the said spring passes one ofthe pins 16 which is projecting from that side of the drum, the spring23 is momentarily forced into contact with spring 22. The arm 21 carriesat its outer end a bell crank 2&, Fig. 7, one end of which is providedwith a pawl 25 which is adapted to be forced into a notch of the ratchetwheel 28 when the end 26 strikes the arm 4:3. The ratchet wheel 28 isrigidly secured to the plate 14. Inside the hollow shaft 19 there issecureda'small is journaled. The other end of the shaft is journaled inthe lug 31 which projects downward from the plate 6. Secured to theshaft 30 there is a ratchet wheel32 which is adapted to be engaged bythe pin 33 which projects from an arm which is attached to the sleeve34. Also secured to the sleeve 34 there is a segment of a gear wheel 35which meshes with a rack 36 secured to the under side of a plate 37which is loosely mounted upon the under side of plate 6. The other endof the sleeve 34 is provided with a flange 38 which lies between therollers 39' and 40 on the end of. arm 41. On the shaft 30 there is asecond sleeve 42 which has a flange projecting between the rollers 39and 40. To the other end of the sleeve 42there is secured an arm 43, theouter end of which is bent at right angles so as to engage the pins 16.From the arm 43 a pin 44 projects through a slot in an arm 45 which issecured to the shaft 30. With this arrangement, the arm 43 is which isjournaled at its lower end in the base 2, and near its upper end in thelug 49 which projects from the plate 6. ,To the upper end of the shaft'48 there is secured an arm 50 which is pivotally secured to the bar 10(Fig. 6). The spring 51 tends to turn the shaft 48 in a counterclockwisedirection, thus holding the end of the arm 43 against the plate 14, andcausing two of the pins 16 to project through the other side of thedrum, as shown in Figs. 11, 12 and 13. The arm 20 which is attached tothe hollow shaft 19 is provided with a pin 52 which projects through anopening in the arm 53. The arm 53 is secured to the shaft 54 which isjournaled in the side pieces 55 and 56 of a clockwork mechanism. To theshaft 54 there is secured a gear wheel 57, to the hub of which there isfastened one end of a coiled spring 58. -The outer end of spring 58 isattached to the inside of a cup 59 which is formed on one face of aratchet wheel 60. The ratchet wheel 60 isloosely mounted on the shaft54. A pawl 61 (Fig. 8) prevents the ratchet wheel 60 from rotatingbackward. The wheel 60 may be rotated forward by means of the solenoid62 through the medium of the arm 63 and pawl 64. Of course, it isevident that, if the wheel 57 is held. stationary while the wheel 60' isbeing rotated, tension will be stored in the spring 58, tending to causethe bushing 29' in which one end of the shaft 30 impulse wheel 67 isprovided with a numher of arms 68 which momentarily press the springs69, 70 and 71 into contact as the wheel revolves. At 72 there isrepresented a' relay which, when energized, forces the end of they arm73 into the path of the arms 68 and shifts spring 74 out of engagementwlth spring 75 and into contactwith spring 76. The speed of operation ofthe mechanism is controlled by the. governor springs,

77. These springs 77; are secured to the worm gear- 78 which registerswith a gear 79 on the shaft 66. When the speed becomes too great theweights oh the ends of the springs 77 move outward and rub on the wallsof thecup 80, thereby producing a braking effect. The relay 72 isprovided with a copper collar 81 around one end of its core, thus makingit slow to denergize when its circuit isjbroken.

The plate 37 which is mounted on the under side of the plate 6 isprovided with a number of laterally projecting arms 82, 82, 82 etc.Figs. 14 and 15 show the under side of the plate 37 together with thelower ends of the push buttons 7. Fig. 14 also shows'the apparatus innormal position, in

which position the distance from the lower ends of the #1 button to thearm 82 is onethird the distance fromthe #3 button to arm 82*, one-fourththe distance from the #4 button to its corresponding arm, etc.

Fig. 15 shows the plate 37 in the position which it assumes when the "#0button is pressed and said plate has moved endwise until the arm 82?strikes the projecting end of said button.

Referring to Fig. 19, it will be seen that the windings of relay 72 andmagnet 62 are connected tothe binding post 87, to which is connected the'non-groulfded terminal of battery B. The grounded terminal of thebattery is connected to binding post 86 and.

' thence to spring '71 and to the frame of the apparatus at 88, thencethrough the arm 20 (Fig. 9) to the spring 23. The spring 22 is insulatedfrom the arm 20, but is connected with an insulated ring 89, through awiper 90. The ring 89 is connected to the winding of relay 72: Thespring 69 is connected with s rin 74 and s rin s 75 and 76 are connect;

P e. P e

ed with the binding posts 84 and 85, respectively, to which the twosides of the line are connected when a call is being made.

The method of operation of the mechanism is as follows: The tension ofthe spring 58 normally tends. to rotate the gear wheel 57. This force istransmitted through the arm 53, pin 52, arm 20, and hollow shaft 19 toarm 21. This forces the end 26 of the bell crank 24 against the end ofthe arm, 43,

forcing the pawl 25 into a notch of the stationary ratchet wheel 28,thereby locking the mechanism. The arm 43 is prevented from rotatingbecause it is held against the plate 14.and therefore engages the sideof one of the pins 16. When the arm 43 is in normal position two of thepins 16 are forced to' the plate 13. Whenever it is desired to call.cession.

9 attached thereto engages the correspond a number, the buttonscorresponding to the digits of that number are depressed in suc- Vhen abutton 'is pressed, the arm ing slot in .the bar 10, forcing the bar tothe le t (Fig. 6). This endwise movement of the bar 10 rotates the shaft48 which,

through the medium of the arm .41, withdraws the end of the arm 43beyond the end of the pins 16 and forces thev pin 33 into a notch of thewheel 32. As soon as the end of the arm 43 clears the pin against whichit has been resting, the spring 47 causes said arm to be rapidlyrotated. This rotation is transmitted through the shaft 30, wheel 32,and pin'33 to the toothed sector 35 which.

meshes with the rack 36. The rotation of the sector causes the rack 36,and consequently the plate 37 to move endwise until.

an arm on the plate 37 strikes the end of the button which has beendepressed. This engagement of the arm of the plate 37 with the buttonlimits the travel of the arm 43. The arms on the plate 37 are so spacedthat whenever any button is pressed, the arm 43 travels just far enoughto pass a number of pins corresponding to the number of the buttonpressed. When the button which has been depressed is released, thespring 51 restores the bar 10 to normal position, forces the arm 43against the plate 14 and withdraws the pin 33 from the wheel 32. lVhenthe pin 33 disengages the wheel 32 the plate .37 is restored to normalposition by the spring 83 (Fig. 6) through the medium of the sector 35and rack 36. When the arm 43 is forced against the face 14 of the drum,two of the pins 16 are forced through the plate 13 into the path of thespring 23, andthe arm 43 is prevented from rotating farther by the nextpin. As soon as the arm 43 disengages the end of the lever 24 when thebutton is pressed, the pawl 25 disengages the ratchet wheel 28 and thearms 26 tioned that each time the spring 23 passes the positionof one ofthe pins 16, the impulse wheel 67 forces the springs 69, 70 and 71 intocontact. The first pin which the spring 23 passes is projecting from theplate 13 so that thefirst time the springs 69, 70

72 and closure of springs 69, 70 and 71 completes a circuit from groundGr through springs 71 and 69, and 74 and 76 to the binding post 85, andthence to the line which is connected therewith. Since the relay 72 isenergized, the arm 73 engages one of the arms of the wheel 67, bringingthe mechanism to rest just after the springs 22 and 23, and 69, 70 and71 are disengaged. Fig. 17 shows the condition of this portion of theapparatus when.the relay 72 is energized, and the springs 69, 70 and 71are in contact. Fig. 16 shows how the impulse wheel 67 is stopped by thearm 73 after said wheel has advanced for enough to allow springs 69, 70and 71 to disengage. The relay 72, being slow acting, holds its armaturein its operated position for a short time, and then allows the" arm 73to be withdrawn from the path of the wheel 67, as shown in Fig. 18. Themechanism then begins to operate again. and the wheel 67 forces springs69, 70 and 71'into contact a number of times,

corresponding to the digit called, each time cred the springs 69, 70 and71 are oncemore forced into contact, and at the same time the springs 22and 23 are brought into engagement because the spring 23 has againreached a pin which is projecting into its path. The relay 72 againoperates in conjunction with the impulse wheel to send a ground impulseto the binding post 85. It will besecn that each time the springs 69, 70and 71 are'forced into contact by the wheel 67. a circuit is closed fromground G through springs 71 and 70 and through the winding of the magnet62 to the nongrounded terminal of battery Each time the magnet 62energizes, it operates to rotate the wheel 60 (Fig. 8) one step torestore the tension to spring 58. i

As the arm 20 rotates it restores'all the operated pins 16 whichit"passes to normal position. Fig. 11 shows the arms 43 and 20 in aposition of rest. Fig. 12 shows arm 43 just after the #1 button has beenpressed and before the arm 20 has had time to start. The arm 43 has beenwithdrawn from its former position, rotated past one pin and then forcedin again and come to rest against, pin 16, causing pins 16 and 16 toproject from the other side of the drum. Fig. 13

shows the condition a little later-that is, just before the arm 20 hascaught up with arm 43. In this position the pin 16 is almost restoredandpin 16 is just beginning to be forced back. With this calling device itisnot necessary that the apparatus shall come to rest after one buttonis pressed and before the next button is operated. The buttonsrepresenting all the digits of any number may be pressed in rapidsuccession. The arm 43 will be rotated in a succession of steps. Eachbutton that is pressed causes the arm 43 to be rotated past a number ofpins, corresponding to the digit called, and then to force two pinsinto' the path of the spring 23 on the arm 20. The arms 20 and 21 thenfollow at a slower speed, one impulse is sent over the line which isconnected to the binding post 85 and the mechanism is stopped for amoment by the relay 72, as has been explained. The mechanism then startsagain, sends a number of impulses, corresponding to the first digit,over the line which is connected to the binding post 84; then the spring23 engages the next pin which was forced into its path by the arm 43,causing another impulse to be delivered to the line which is connectedto the binding post 85, after which the mechanism will be momentarilystopped by the relay 72. This cycle of operations is repeated in turnfor each digit until the arm 21 catches up with the arm 43. With thisarrangement the impulses for each digit consist of one impulse over oneside of the line, then after a pause a number of impulses are sent overthe other side of the line, followed by a sec ond impulse over the firstside, then after a short interval of time, the impulses for the nextdigit are transmitted in the same order.

In order to give a clearer understanding of the operation of the callingmechanism, reference may be had to the diagrammatic drawing (Fig. 20).In this figure the various circular parts of the mechanism, such as thecentral drum with its circular row of pins 16 and the ratchet wheels 32and 60, are shown developed into a straight line, and the movable artsare assumed to have a rectilinear motlon. The arrows on the variousparts show the direction of their movements. The double headed arrowsrepresent movement in both directions. The impulse wheel 67 isrepresented in this figure by a straight bar provided with a pluralityof "impulse teeth. Referring to this fi re, the mode of operation is asfollows:

I pon pressing one of the buttons 7 the'bar 10 is forced to the left,thereby causing the arm 43 to be lifted above the top of the pins 16 andthe catch 33 on' the member 37 to be lifted into engagement with theteeth in the ratchet wheel 32. As soon as the end of'the bar 43 islifted above the top of the pins 16,

the spring-47 forces said bar to theright until one of the projectionson the member 37 engages the lower end of the push button whlch wasdepressed. When this occurs,

the bar 43 will have passed completely over a number of pins 16corresponding to the button pressed. When the button is released, thebar 10 returns to its normal position, whereupon the catch 33 isdisengaged from the wheel 32 and the member 37. restored to the left toits normal position by the spr1ng,83,and the bar 43 causes two of thepins 16 to be pushed through the drum. As soon as the bar 43 leaves thearm 21, the shaft 19 begins to be drawn to the right by the spring 58,its movement, however, being retarded by the governor 77. Upon theinitial movement of said shaft, the finger 22 engages one of the pinswhich was depressed by the bar 43 in its original position, whereby thecircuit of the slow acting relay 72 is closed. The relay 72, uponenergizing, moves the locking member 73 into the teeth on the impulsewheel 67 and places the spring 74 into contact with the spring 76. Afterthis occurs, the shaft 19 still moves to the leftfar enough to disengagethe finger 22 from the pin 16 and to cause the spring 71 to make andbreak contact with the springs 69 and 70 before the impulse wheel isbroughtto rest by the stop 3. The engagementof the springs 71 and 69while the relay 72 is energized transmits a single ground impulse to theline conductor 85. After sending this impulse, the shaft 19 remains atrest until the slow act- 100 ing relay 72 has had time to deenergize towithdraw the locking member 73 from the impulse wheel 67. When thisoccurs, the shaft 19 resumes its movement, during which a series ofimpulses are transmitted 05' from ground through the springs 71, 69, 74and 75 to the line conductor 84. After a number of impulsescorresponding to the push button which was depressed has thus beendelivered to the line 84, the finger 22 0 engages the first pin whichwas depressed by the arm 43 in its advanced position, and transmitsanother impulse through the slow acting relay 72. The relay 72 operatesin the same manner as before to cause a single 1'15 7 impulse to betransmitted to'the conductor 85 and then to momentarily bring themechani'sm'torest. If, before the mechanism has been brought to rest,the'second button has been pressed, the same cycle of operations abovedescribed will be repeated when the' relay 72 deenergizes. If no otherbutton has been depressed, the shaft 19 will simply move forward a shortdistance upon the deenergization of the relay 72, when it will bebrought'to rest by. the engagement with the arm 43".

The manual substation A (F g. 1) with which I have elected to illustratemy invention may be of any suitable type, but, as

herein illustrated, comprises the usual receiver 91, transmitter 92,switch hook 93, finger 94 and condenser 95. At the central office thereis allottedto thelineof substa-- tion A two conductors j and 7' acut-off relay 97, line relay 98 and line lamp 99.

The operators cord C may also be of any suitable type. As hereinrepresented, the

cord C is a well known type of cord circuit,

modified slightly to adapt it foruse either in connecting two manuallines or connecting a manual line with an automatic line. The answeringend ofthe cord comprises a plug 79, two supervisory relays 100 and'lOland a signal lamp 102. 'A battery B is'provided for the purpose offurnishing current for operating the relays and for talking. The callingend of the cord is provided with 'a plug 12 two relays l103 and 104, anda lamp 105. A push button 252 is provided through the springs of whichthe relay 104 is normally bridgedbetween the two sides of the cord. Whenthe button is in its depressed position the bridge through relay 104 isopened, and the two sides of the cord are connected to the oppositeterminals of the battery through the relay 103 and impedance coil 153.

The calling end of the cord is also equipped with the usual ringing andlistening keys K and K, and with-a calling device key K by means ofwhich a calling device similar to that shown in Figs. 5 to 19,inclusive, may be connected with the cord. In Fig. 1 the calling deviceis represented simply by a circle 106. l

The trunk lines leading to the automatic exchange are provided with oneor more jacks'f, j etc., with each of which there is associated a busysignal lamp 107. Each trunk line is also provided with two relays 108and 109 which operate to ca-usethe release of the automatic switcheswhen the plug is removed from the jack.

The trunk switch D, Fig. 2, issimilar to the line switch disclosed inBritish Patent #26301, of. 1906 and in the AmericamTeZephone Journal ofNew York, N. Y., of June '6, 1908. Among other details it comprises aplunger (not shown) adapted, when released by the energization of.thet'rip magnet 110, to operate some one group of .a

a number of grou s of springs 111, 112, 113,

1144, 115, 116, 11 and 118. The plunger is restored to normal positionby the energization and deenergization of the release magnet 119.

The plungers of a number of line switches D are controlled by a masterswitch E, which is -a.sl1ghtlymodified form of the general type ofmasterswitch disclosed in the said British Patent #26,301.of 1906, andthe American Telephone J oumal of June 6, 1908. It comprises essentiallya motor magnet 253 for operating the ratchet Wheel 254,

any suitable type. substation A is provided with the usual rapes and abank of contacts comprising an individual contact a for each trunk towhich the switch D has access and a common segment 255. The ratchetwheel254 is connected to the so-called plunger shaft (not shown) in such amanner that the rotary motion of said wheel transmits to the plungershaft an oscillatory motion to move the plungers that are engagedtherewith back and forth in front of the trunk terminals. The circuit ofthe motor magnet 253 is controlled by the relay 120 and also by springs121. and 122. The springs 1213and 122 are controlled by the notchedwheel 123 in such a manner that said springs can be disengaged only whenthe plungers that are en gaged withthe plunger shaft are directly infront of the terminal of a trunk line. The wiper 12 1 is attached to theplunger shaft and is adapted to always keep the segment 255 inelectrical connection with the contact a which belongs to the trunk linebefore which the idle plungers are being held by the plunger shaft.

The selectors F and H are of the wellknown Strowger type disclosed inUnited States Letters Patent #815,321, granted March 13, 1906, to Keith,Erickson &

Erickson.

The connector I is of the general type dis closed in United StatesLetters Patent #815,17 6, granted March 13, 1906, to Keith, Erickson &Erickson.

The automatic substation A may be of As herein illustrated, the

receiver 125, transmitter 126, induction coil 127, switch hook 129, andringer 130. To adapt the substation A for operation in an automaticsystem it is also provided with two impulse springs 1'31 and 132 and animpulse wheel 133 which is secured to a shaft 134, to which there isalso secured a dial (not shown) provided with finger holes.

In the diagrammatic representation of the system shown in Fig. 4, Mrepresents a section of a manual switch board upon which .terminate thelines of "a group of substations A. This section of the board isprovided with a number of cords C and one of my improved callingdevices, represented at a. In thisfigure there is also represented agroup of automaticsubstations A terminating at an automatic exchange 1nline switches D These line switches have access to selector switches F..In this figure the bank contacts-of the selector switches and connectorsare represented by three horizontal lines representing three differentlevels. -A group of second selector switches H and connectors I is alsoshown. On the manualboard M there is shown group of jacks j with thetrunk lines leadlng there- .from to trunk switches D at the automaticexchange. Of course, it is to be understood that the manual board mightconsist of a number of sections similar to that shown here, and that theautomatic exchange might comprise a number of groups of lines, withtheir accompanying line, selector and connector switches.

In the drawings a plurality of batteries B are shown. Only one batterymay be used,

however, or, preferably, one in each exchange.

Having given a general descrlptlon of the apparatus, I Wlll now explainhow a connection is established between the substations A into the jack7', whereby a circuit is closed extending from ground G through thecutoil relay 97, sleeve of jack j and plug 10 and through relay 101 tothe battery B. The relay 97, upon energizing, disconnects the ground Gand relay 98 from the calling line and extends said line through thejack j and plug 19 to the cordC. The relay 101., upon energizing,connects the lamps 102 and 105 to the non-grounded pole of batteryB. Thelamp 105 is lighted by this action, but the circuit of lamp 102 ismaintained open by relay 100. After ascertaining that a subscriber ofthe automatic exchange is desired, the operator inserts the plug p intothe jack j 'and operates the key K. The insertion of the plug 19 intothe jack 7' connects'the cord C with a trunk line leading to a trunkswitch D of the automatic exchange, and by closing contact betweensprings 135 and 136 causes the busy signal lamp associated with eachjack belonging to this trunk to be lighted. The closure of contactbetween springs 135 and '136 also closes a circuit I through the relay108 which, uponenergizing, in turn closes a circuit through relay 109.These'two relays remain energized until the plug 19 is removed.- Theoperation of the key K previously mentioned disconnects the plug 37 fromthe cord and connects the calling device 106 with the trunk line leadingto .the automatic exchange. The so-called vertical side of the trunk 137is connected with the binding post 84 of the calling device, and therotary side of the trunk 138 is connected with binding post 85. Assumingthat the number of the substation desired is #2220, the operator nowpresses the #2 button three times and the #0 button once. The callingdevice then operates in the manner explained totransmit the requiredground impulses for causing the automatic switches to extend theconnection to line #2220. The first impulse is transmitted from groundthrough binding post 85, over trunk conductor 138, through springs 139,140 and 141 of switch D (Fig. 2), trip magnet 110 and springs 142 and143 to battery lead 144, thence through the battery B to ground G. Theenergization of magnet 110 allows the plunger of the switch D to bereleased to press springs 111, 113,115 and 117 into contact with springs112, 114, 116

- and 118, respectively. The engagement of springs 115 and 116 completesthe energizing circuit for the cut-off relay 146, which operates todisconnect the trip magnet 110 from the trunk conductors 137 and 138.The engagement of springs 111 and 113 with the springs 112 and 114extends the trunk conductors 137 and 138 through to the selector F. Theengagement of springs 117 and .118 completes an energizing circuit forthe motor magnet relay 120 of the master switch E. This circuit extendsfrom ground G through relay 120, segment 255, wiper 124, contact point147 which corresponds to the trunk seized by the switch D, thence overconductor 148 and through springs 118 and g 117, release magnet 119 tobattery lead 144. The relay 120 is energized over this circuit, butbeing of comparatively high resistance, does not permit sufficientcurrent to flow to energize the magnet 119. The relay 120, uponenergizing, completes a circuit extending from ground G thiough relay149 and motor magnet 253' in multiple, interrupter springs 150 and relaysprings 151 and 152 to battery lead 144. As soon as this circuit isclosed the motor magnet 253 begins to operate in a manner similar tothat of a' buzzer toqmoy e the plungers of the idle switches D away fromthe trunk just seized. As soon as the ratchet wheel 254 has been movedone step by the magnet 253, a tooth on the wheel 123 forces springs 121and 122 into contact, thereby maintaining the circuit of magnet 253independently of relay 120.

v The motor magnet continues to advance the plungers until the spring122 drops into the next notch of thewheel 123, whereby the circuit ofthe magnet 253 is'broken, since by this time the wiper 124 has passedoff of contact point 14'] and allowed relay 120 to deenergize. If thenext trunk after the one just seized by the switch D has been busy, thewiper 124 would have found the next contact connected tobattery throughits corresponding release magnet, the relay springs 152 and 151 wouldstill have been in engagement when springs 121 and 122 were separatedand the idle plungers would have been carried on to an idle trunk. Itwill be remembered that the relay 149 was included in an energizingcircuit in multiple with magnet 253. The relay 149 is slow acting andconsequently does not have time to denergize during the short intervalswhen its circuit is opened at the interrupter springs 150. Thus therelay 149 remains in its operated position during the entire time themaster switch is operating, thereby disconnecting the battery from thetrip magnets 110 of all the trunk switches D of thisgroup, so that noswitch can be operated while its plunger is moving.

As has been previously explained, after an impulse is sent over the linewhich is connected with the binding post 85, the mechanism of the.calling device stops for a short time, and then sends two impulses overthe other side of the line. These two impulses pass out of the callingdevice through binding post 84, thence over trunk conductor 137, banksprings 111 and 112 of switchl), side switch wiper 154 and vertical linerelay 155 of the selector F to the battery lead 144.- Each time therelay 155 is energized a circuit is closed throug the vertical magnet156. This circuit extends from ground G through springs 157 and 158, 159and 160, and magnet 156 to battery lead 144. Since the digit called is 2the vertical magnet 156 receives two im-r pulses over the circuit justtraced, operating to raise the switch shaft and wipers 161, V162 and163two steps to a position opposite the second row or level of bankcontacts. A second impulse is now sent in over the rotary trunk 138,passing through springs 113 and 114, side'switch wiper 164 of selector Fand rotary line relay 165 to batterylead 144. The relay 165,uponenrgizing, closes a circuit from ground G through springs 157 and166 and private magnet 167 to battery lead 144. The private magnet, uponenergizing and deenergizing, permits the side switch wipers to pass fromfirst to second position in a well-known manner. When side switch wiper168 engages its second-position contact point a circuit is extended fromground Gr through said wiper 168, interrupter springs 169 and 1 rotarymagnet 170 to battery lead 144. The

rotary magnet thereupon attracts its armal ture, which rotates thewipers 161, 162 and 163 one step, presses down the armature of theprivate magnet 167 and opens the circuit of its own magnet at theinterrupter springs 169. When the rotary magnet circuit is thus opened,the rotary armature dropsback, and if the first trunk line of the secondlevel is idle, the armature of the private magnet falls back also,allowing the side switch to pass'to third position. "If the first trunkis busy, however, on account of having been seizedby some other selectorsimilar to selector F, a locking circuit is closed through the privatemagnet 167.

. This circuit extends from ground through the other occupying switch(not shown pr vate bank contacts of the busy trunk,

dium of its interrupter springs, until it has battery lead 144.Sufficient current does not flow over this circuit to energize the relay172, but the private magnet armature is held in its operated position,thus locking the side switch in second-position. The rotary magnet 17 0then continues to be alternately energized and denergized through themerotated the wipers onto the terminal of an idle trunk, whereupon theprivate magnet 167 becomes deenergized and allows the side switch topass to third position. When the side switch wiper 168 leaves its secondposition contact point, the operating circuit of the rotary magnet 170is broken. The passage oftthe side switch .wipers 154 and 164 fromsecond to third position disconnects the relays 155 and 165, from theline and extends the connection through to the second selector H. Also,as soon as the side switch reaches third position, the seized trunk isprotected from being seized by another switch, by a guarding potentialextending from ground G through side switch wiper 173, relay 17 2 andprivate wiper 162 to the private bank contacts bf the busy trunk in thebanks of all switches by which it is accessible. 7 After the last rotaryimpulse for the first 'digit 2- is sent in, the impulse mechanismswitches are so constructed that the side switch cannot leave firstposition until after the vertical magnet has been operated one or moretimes, and it cannot leave second position until the shaft has beenrotated one or more steps. The reliminary rotary impulse for the firstdigit is used to operate the trunk switch D. The vertical impulses forthe second digit pass from ground at the calling device 106 over trunkconductor137,

through switches D'and F, and through the vertical line relay 1750f theselector H to battery lead 144. The selector H, operates in response tothese impulses in the same manner as explained for the selector F toraise its wipers 176, 177 and 178 two steps. The next impulse over therotarytrunk conductor 138 passes through the selector F and throughtherotary relay 179 of' the selector H. The relay 179 causesthe privatemag- A net 180 to trip the side switch from first to '-second positionjust as in the case of the selector F. The wipers of the selector H arethen rotated onto the terminals of a trunk line comprising conductors181, 182 and 183 which lead to an idle connector switch I (Fig. Theconnector I then operates in accordance with the impulses for the lasttwo digits to complete the connection with the called line. The circuitfor the two vertical impulses for the third digit 2 extends from groundat the calling device, over conductor 137, thence through the verticalline wipers 161 and 176 of selectors-F and H,

. over trunk conductor 181 and through the vertical line relay 184 andupper winding of relay 185 of the connector I. The energization of relay185 in response to these impulses is without function. Each time thevertical relay 184 is energized, however, a circuit is completedextending from ground G through springs 186 and 187, springs 188 and189, side switch wiper 190 and vertical magnet 191 to battery lead 144'.The vertical magnet 191 receives two impulses over this circuit,operating to raise the wipers 192, 193 and 194 two steps to a positionopposite the second row or level of their respective bank contacts.After the vertical magnet has completed itsoperation, the rotary linerelay is energized by an impulse from ground at the calling device 106,over trunk conductor 138, through switches F and H,'over trunk conductor182 and through relay 195 and lower winding of relay 185 to battery lead144. The relay 195, upon energizing and. deenergizing, sends an impulsefrom ground G through springs 186 and 197, private magnet 198 andsprings 199 and 200 to battery lead 144. The private magnet 198 operatesin response to this impulse to cause the side switch to pass from firstto second position. In its second position, the side switch wiper 190places the vertical line relay 184, in control of the rotary magnet 201instead of, the vertical magnet 191. The ten impulses for the last digitnow pass through the relay 184 which operates to close the circuit ofthe rotary magnet 201 ten times.

With the exception of the magnet itself, this circuit is the same asthat traced for the vertical magnet 191. The operation of the rotarymagnet causes the wipers 192, 193 and 194, to be rotated ten steps ontothe contacts of the called line. The final rotary impulse for the lastdigit causes the rotary relay 195 to again close the circuit of theprivate magnet 198, which in turn operates to cause the side switch topass to third position, whereby the connection is extended to the calledline by the wipers 202 and 203. The engagement of side switch wiper 204with its third-positioncontact point pro-- vides a guarding potentialupon the con nector..- rivate bank contacts of the called line, andcloses an energlzing circuit for the cut-ofi' relay 205 of the lineswitch D This guarding potential and energizing circuit extends romground G through side switch wiper 204, private wiper 194 and contactupon which it is resting, and thence to the corresponding contacts inthe banks of all tions are united over the heavy conductors shown in-thedrawings. In order to signal the called line the operator presses thebutton K after the key K is restored.

'Whenthe button K is pressed it opens the bridge across the trunkthrough the relay 104 and grounds the vertical trunk conductor .137. tor137 causes the energization of the connector relays 184 and 185 in thesame manner in whichthey were energized by the impulses for the last twodigits. Since the side switch is now in third position, the energizationof relays 184 and 185 completes a circuit from ground Gd through springs186 and 187, 188 and 189, side switch wiper 190, ringing relay 210 andsprings 211 and 212 to battery lead 144. The relay 210 upon energizing,shifts spring 213 out of engagement with spring 214 and into contactwith spring 215, and forces spring 217 into engagelnent with spring 216.-By this operation the connection between the calling and called linesis opened on one side and the ringing generator L is bridged across thecalled line to ring the bells 130. WVhen the called subscriber removeshis receiver in response to this signal, the circuit. of the ringer 130is broken by the separation of springs 218 and 219 and the primarytalking circuit is bridged across the line by the engagement of springs220 and 221. When this occurs the called substation is provided withtalking battery current over a circuit extending from ground G at theconnector I through side switch wiper 204, lower The grounding of theconduclead 144.

this circuit and operates to shift the connection of the lower windingof relay 185 from the battery lead 144 to ground at G through sideswitch wiper 204. By this action a circuit is. completed from ground Gthrough side switch wiper 204, springs 229 and 199, lower winding ofrelay 185,

rotary relay 195, trunk conductors 182 and '138, sleeve of ack j andplug p, relay 104,

springs 230 and 231, tip of plug p and jack j trunk conductors 137 and181, relay 184 and upper winding of relay 185 to battery In thisinstance the current passes through the two windings of relay 185 inopposite directions, thereby producing no effect. The relays 184 and 195are both energized, but without function at this time. At the cord C therelay 104 is ener-- gized to break the circuit of lamp 105,

, called subscriber has answered.

which signifies to the operator that the The hanging up of the receiverat the called substation after the conversation is completed destroysthe circuit Of the connector back-bridge relay 222. This relay 222, upondenergizing, breaks the circuit ofthe supervisory relay 104 at the cordC, which relay allows its armature to fallback, causing the lamp 105 tobelighted, and thus giving the operator a disconnect signal. Theoperator receives a seconddisconnect signal when the calling subscriberhangs up his receiver, thereby breaking the circuit of the relay 100,which allows its armature to fall back to close the circuit of lamp 102.The;

operator thereupon removes the plugs, 12 and p.

The removal of the plug p from'the. ack j destroys thecircuits o-f thebusy lamps 107 and of the relay 108. The relay 108, upon deenergi'zing,connects the ground G with both of the trunk conductors 137 and 138 andbreaks the circuit of relay 109. The relay 109being slightly slow actingholds its armatures in their operated position for a shorttime after therelay 108 is dee'nergized, and then allows them to drop back to'removethe ground connection'from the trunk conductors 137 and 138. Thegrounding of the conductors 137 and 138 causes the connector line relays18.4 and 195 to be energized over circuits which have already beentraced. The relay 185 is also energized at this time, since currentflows through both of its windings ih the same direction. Thesimultaneous energization of relays 184, 185 and 195 completes a circuitfor the connector release magnet 232, said c1rcu1t extendlng from groundG at the selector H, through side switch wiper 233, release relay 234,private wiper 178, conductor 183, springs 235 and 236, release magnet232 and springs 211 and 212 to battery lead 144. The releasemagnet 232,upon 'enerigizing, causes the connector I to be immediately restored tonormal posiother call.

tion, whereupon the cut-off relay-205 of the line switch D becomesdeenergized also. The energization of the release relay 234 of theselector H completes a-circuit forits release ma 'net 237. This circuitextends from ground 5 at the selector F, through side switch wiper 173,relay 172, private wiper 162, springs 238 and 239, and magnet 237 tobattery lead 144. The energization of the relay 172 of the selector Fcompletes an en ergizing circuit for the releasemag'net 240. Thiscircuit extends from ground Gi through springs 241 and 242 and magnet240 to bat-- tery lead. The magnet 240, u on energizing, closes acircuit from'ground 5 through contact point 243, ar'mature'244, springs118 and nets 119,- 240 and 237 of the switchesD and H hold theirarmatur'es in position to 117, and release magnet 11-9 of the switch I)to thebattery lead 144. The release mag:

release their respective switches when their circuits are brokenfollowing the deenergization of the trunk-release relay 109 (Flg. 1),whereby all apparatus employed in the connection is left in readinessfor use in an- The foregoing is anexplanation of how connectionisobtained with an idle line. In

case a line is already in use when it is called, connectionis notcompleted therewith, and the calling subscriber receives a busy signalas follows: It has been shown that when a line is busy there is aguarding ground po-.

tential at the private contact of that line in the bank of eachconnector to which itiis ac -cessible. In case the wipers of theconnector I are resting upon the contacts of a busy and therefore aguarded line when the final rotary impulse for the last, digit isdelivered, the sideswitch does not pass to third position, but theconnector is released. The circuit for the release magnet in thisinstance extends from the guarded private bank. contact, through wiper194, side switch wiper 204 (which would then be in'second position),springs 245 and 246 .of the private magnet 198 (the circuit of which isclosed in the usual manner by the operation of the rotary relay195),magnet 232, and springs 211 and 212 of relay 185 (which is alsoenergized by the rotary impulse), to battery lead .144. Since theconnector is in normal position when the ringing button at the cord C ispressed the consequent grounding of the vertical side of the line causesthe vertical magnet 191 of the connector to be op-' "erated in a mannerwhich has already been.

explained. As soon as the shaft of the connector is raised one step, thesprings 247 .and 248- are closed into contact, whereby the busysignaling machine N' is connected with the calling line.

The circuit OTr'l' which the busy signaling current flows extends fromthe battery lead 144 through the secondary winding of the induction coil249, springs 0

